Research On Warm Island In Badain Jaran Desert Based On Observation Data

The megadune in Badain Jaran Desert is the heightest in the desert of the word, among these megadunes dotted with many lakes, and the megadunes and lakes alternatively distributed in Geomorphology. The sources of lakes recharge, the cycle of lakes water and the formation and evolution of high sand dunes are scientific problems, which had been concerned and researched at home and abroad.It has been reported that the winter land surface temperature in the lake region of the Badain Jaran Desert was warmer than the peripheral region and desert surrounding region. The same phenomenon has been found through several field investigations. Considering the limits of continuous observation by using remote sensing data, it should be combined with observations of land surface processes to reveal the “warm island effect” and its formation mechanism. It will be of important significance for the study on the mechanism of recycle of lake water, the sources of groundwater recharge, land surface processes, ecological system and human activities.In this paper, we select six observation experiment stations’ data in the hinterland of the Badain Jaran desert and several national meteorological stations’ data in the desert surrounding region area, including daily average temperature, ground temperature, sunlight, radiation and other factors. Then we compared each meteorological element between the hinterland and its surrounding areas to revel the “warm island effect” in the lake region of Badain Jaran Desert and primarily probed its mechanism. The main findings and preliminary conclusions are as follows:(1) The annual and seasonal mean temperature and the heat resource are higher in the lake region of Badain Jaran Desert than that in the surrounding areas. First, the annual average temperature and monthly average temperature of January, April, July, October is 1℃,0.9℃, 1.2℃, 0.8℃, 1.5℃ higher separately than that in the surrounding areas. Second, the starting date of spring and summer is 2days and 3 days earlier and the ending date of autumn and winter is delayed 9 days and 4days in the lake region of Badain Jaran Desert than that in the surrounding areas. Thereby the length of summer is 12 days longer, the length of autumn is 5 days shorter, the length of winter is 6 days shorter in the lake region of Badain Jaran Desert than that in the surrounding areas. Third, the starting date of ≥0℃ accumulated temperature was 2days earlier, the ending date of ≥0℃ accumulated temperature was 9 days delayed, the duration days of ≥0℃ accumulated temperature are 11 days longer and the ≥0℃ accumulated temperature is 413.8℃ higher in the lake region of Badain Jaran Desert than that in the surrounding areas. The starting date of ≥10℃ accumulated temperature is 4 days earlier, the ending date of ≥10℃ accumulated temperature is 6 days delayed, the duration days of ≥ 10 ℃ accumulated temperature are 10 days longer and the ≥10℃ accumulated temperature is 420.3℃ higher in the lake region of Badain Jaran Desert than that in the surrounding areas. At the same time, the winter negative accumulated temperature ≤0℃ is 96.0℃ higher and the duration days of negative accumulated temperature ≤0℃are 2days shorter in the lake region of Badain Jaran Desert than that in the surrounding areas.(2) Due to the high albedo in desert surface makes its annual and seasonal average surface temperature is lower than that in the surrounding areas, the annual average surface temperature and monthly average surface temperature of January, April, July, October is 1.6℃,2.9℃, 1.9℃, 0.1℃, 1.5℃ lower separately than that in the surrounding areas. Due to the the site in desert hinterland is located in lake basin area, the sunshine hours are less in winter in the lake region of Badain Jaran Desert than that in the surrounding areas. But the differences is small in other seasons.(3) The mechanism of "warm island effect" in Badain Jaran desert is related to two aspects. first of all, due to the sparse vegetation in the desert and less caloric expenditure through transpiration, most of the net radiation to the atmosphere through sensible heat flux. So the temperature is higher and the heat resource is richer in the lake region of Badain Jaran Desert than that in the surrounding areas although the difference of the annual and seasonal net radiation is small. Second, negative feedback effect of sand-radiation in desert hinterland is one of the reasons that lead to its high temperature; Third, during the process of deep groundwater recharged lakes, much heat was being carried from the groundwater. It is also an important cause for the "warm island effect", but the magnitude order need to be further explored.(4) As for the difference of heat between stations in the hinterland, it may be related to the micro-climatic environment, the megadune strikes and the size of lake basins in the location of meteorological stations. The concrete reason which causes the difference still needs more researches. Since V4 station in Baxingaole is located in the surrounding area, it did not appear the phenomenon which is occurred in the lake region of Badain Jaran Desert and it is in line with the law of the surrounding areas of the desert. It also suggested that observation experiment stations’ data in the hinterland of the Badain Jaran desert is accurate and reliable and it can be compared with the national meteorological stations’ data.